1. Technical Field
The present invention relates to a vertical cavity surface emitting laser and an atomic oscillator.
2. Related Art
A vertical cavity surface emitting laser (VCSEL) is, for example, used as a light source of an atomic oscillator using coherent population trapping (CPT) which is a type of quantum interference effect.
In the vertical cavity surface emitting laser, a resonator generally has an isotropic structure, and accordingly it is difficult to control a polarization direction of the laser light emitted from the resonator. JP-A-2001-189525, for example, discloses a vertical cavity surface emitting laser which applies an anisotropic stress to a resonator (active layer) by an insulation layer which is formed to come in contact with an outer surface of a columnar semiconductor deposition body including apart of the resonator, and controls a polarization direction of laser light to a specific direction.
However, in the vertical cavity surface emitting laser disclosed in JP-A-2001-189525, it is difficult to apply sufficient stress to the resonator by the insulation layer, and the polarization direction of the laser light may not be stabilized.